As a method of forming a thin film in which a predetermined thin film is formed on a surface of a process substrate such as glass, there is a sputtering method. Particularly in the sputtering method of magnetron system, by arresting electrons generated by ionization in front of a target and secondary electrons generated by sputtering, the electron density in front of the target is enhanced and the probability of collision of these electrons with gas molecules of an inert gas to be introduced into a vacuum chamber is enhanced to thereby increase the plasma density. Therefore, this method has an advantage in that the film forming speed can be improved and the like and is often utilized in forming a predetermined thin film on a surface of a process substrate. Recently, this method is quite often utilized in forming a predetermined thin film on a substrate that is large in area such as a glass substrate for manufacturing a flat display panel (FDP).
As an apparatus for efficiently forming a predetermined thin film at a constant film thickness on a process substrate having a large area, there is known a sputtering apparatus in which a plurality of targets of the same shape are disposed inside a vacuum chamber in parallel with one another. In this sputtering apparatus, however, the sputtered particles are not emitted from the region between the respective adjoining targets. Therefore, if a predetermined thin film is formed on the surface of the process substrate, the film thickness distribution of this thin film and the film quality distribution at the time of reactive sputtering become non-uniform in an undulated manner (e.g., in the film thickness distribution, a thicker part and a thinner part are repeated in the same cycle).
As a solution, it has been proposed to improve the non-uniformity in the above-described film thickness distribution and the film quality distribution by: integrally reciprocating each of the targets in parallel with the process substrate at a constant speed while electric power is supplied to each of the targets to form the thin film by sputtering; and thus changing the regions in which the sputtered particles are not emitted, as a result of integrally moving each of the targets, in other words, by causing the entire surface of the process substrate to lie opposite to the region in which the sputtered particles are emitted from the surfaces of the targets. In addition, in order to further enhance the uniformity in the film thickness distribution and the film quality distribution, it has also been proposed to reciprocally move a magnet assembly disposed to form a magnetic flux of tunnel shape in front of each of the targets, in parallel with the target and at a constant speed, thereby changing the position of the tunnel-shaped magnetic flux in which sputtering rate becomes high (patent document 1).    Patent Document 1: JP-A-2004-346388 (see, e.g., what is described in claims).